1. Idaho became the 43rd state of the United States on July 3, 1890, but it wasn't until December 21, 1890, that the state's constitution was formally signed into law and the state officially came into being. This historic moment took place in an elaborate ceremony at the newly constructed state capitol building in Boise.

2. On December 21, 1914, the first natural gas well in Idaho was discovered near the town of Burley in the southern part of the state. The well was drilled by a local businessman named W.D. Kiesel, who recognized the potential of the natural gas reserves in the area. Today, natural gas is a major industry in Idaho, providing fuel for homes, businesses, and industry.

3. In 1937, the famous American aviator Amelia Earhart made a stop in Boise on December 21 as part of her around-the-world flight. Earhart was the first woman to fly solo across the Atlantic, and her visit to Idaho was a major event for aviation enthusiasts in the state. She gave a speech at Boise's Municipal Airport before continuing on her journey.

4. December 21, 1987, was a significant day in the history of the mining industry in Idaho. On that day, the Sunshine Mine in Kellogg experienced one of the worst mining disasters in American history when a fire broke out underground, killing 91 miners. The tragedy sparked a renewed focus on mine safety and led to improved regulations and equipment for miners across the country.

5. Finally, on December 21, 2017, Idaho made history by becoming the first state to allow the legal use of cannabis-based medicines to treat epilepsy in children. The law, known as "Alexis's Law," was named after a young girl from Boise who suffered from severe seizures that could only be controlled with medical marijuana. The law allows parents to administer non-psychoactive forms of cannabis to their children under the guidance of a doctor.